Question

Are there any easy ways to debug forked child processes in *nix, without having to sleep them and create new gdb instances, using ps to get the child’s pid? Are there any debuggers that do this?

Answer 1

You can already do this using gdb. Here is how:

(gdb) set detach-on-fork off
(gdb) set follow-fork-mode child
(gdb) catch fork # use breakpoint if catch fork not available

Then at some point you will reach your fork. Jump over it and gdb should inform you there is a new process.

[New process 813]

At this point you should view the “inferiors”

(gdb) info inferiors
  Num  Description       Executable
* 2    process 813       /home/cnicutar/fork
  1    process 810       /home/cnicutar/fork

To switch to a different inferior, use

(gdb) inferior 1
[Switching to inferior 1 [process 810] (/home/cnicutar/fork)]
[Switching to thread 1 (process 810)]

(gdb) info inferiors
  Num  Description       Executable
  2    process 813       /home/cnicutar/fork
* 1    process 810       /home/cnicutar/fork

Hope this helps 🙂